This invention relates to communication switching systems and an optically based switching element that uses MEMS modification of the electromagnetic radiation signal wavefront to effect the signal switching function.
It is a problem in the field of communication switching systems to provide signal switching apparatus that is faster in operation, smaller in size, more robust, and less expensive than the signal switching apparatus presently used in existing communication switching systems. The state of the art in existing communication switching systems is the use of transistor based signal switching elements to implement electronic switching of the received electrical signals. These transistor based signal switching elements receive the electrical signals that represent the communication signal from an input port and then redirect these electrical signals to a selected one of a plurality of output ports. The interconnection of the input and selected output ports is effected in a manner that the electrical signals may be transmitted in unmodified form.
As optical signal transmission elements are propagated into these communication switching systems, the need to convert the optical signals to electrical signals and back again to implement the signal switching function represents a significant inefficiency in the operation of these systems. Since most communication connections require many stages of switching, the seriatim conversion between electrical and optical format of the communication signals reduces the benefits provided by the optical transmission of the communication signals. An alternative to the signal conversion paradigm is to provide an all-optical communication switching system. However, the signal switching elements used in existing all-optical communication switching systems suffer from a number of problems, including but not limited to: lack of speed, materials related issues, limited scaling potential, and the like. Therefore, there is presently no signal switching element in all-optical communication switching systems that can efficiently compete with transistor based signal switching elements, in spite of the limitations noted above.
The above described problems are solved and a technical advance achieved by the present switching system with MEMS modification of a signal wavefront which implements a new type of all-optical signal switching element that uses the coherence properties of electromagnetic radiation, coupled with the materials properties of semiconductors through the application of existing Micro-machined Electro-Mechanical System (MEMS) technology to provide signal switching apparatus that is faster in operation, smaller in size, more robust, and less expensive than existing signal switching elements found in all-optical communication switching systems. This is accomplished by the use of a semiconductor chip that has a MEMS mirror system implemented on its face. The MEMS device is constructed to operate in a pure materials flex mode, with no moving mechanical parts to wear. The MEMS mirror system is used to create local distortions in the reflected and/or transmitted electromagnetic radiation wavefront to redirect the electromagnetic radiation in such a way as to create channels of changed resistance or index of refraction in a bulk semiconductor. These changes in resistance to the channels serve to enhance or impede the motility of electrons through the bulk semiconductor, thereby providing an electrical switching function within the bulk semiconductor. Alternatively, the redirection of the input electromagnetic radiation wavefront can be effected via changes in the index of refraction in the bulk semiconductor material.
In this system, the coherent electromagnetic radiation (such as a beam of light) from a source is split into two beams: a reference beam and an object beam. The object beam is directed at the surface of a semiconductor wafer that has been modified to create a plurality of MEMS surfaces whose position can be altered through the application of a suitable voltage to the semiconductor wafer. The application of this voltage alters the position of the surface of the selected MEMS device with respect to the semiconductor wafer by either tilting the surface of the MEMS device or by vertically repositioning the surface of the MEMS device relative to the semiconductor wafer. This repositioning of the selected MEMS device imparts a phase front delay and possibly an intensity modulation of the redirected wavefront that travels in certain directions on the portion of the electromagnetic radiation wavefront of the object beam that is transmitted through or reflected from the surface of the MEMS device relative to the reference beam of the original signal. The phase front modified object beam is used to either interact with the reference beam in the volume immediately above or below the MEMS surface, as is typical in reflection holography or alternately is combined with the reference beam as is typical in transmission holography. In either case a controllable, three dimensional, volume spatial fringe pattern is formed due to the variation in the two beams introduced by the operation of the MEMS device. The volume spatial fringe pattern is made up of one or more spatial volumes that can be used in one application to create the channels of changed resistance in a bulk semiconductor.